Subject: Re: [PATCH v18 08/15] userfaultfd: untag user pointers

From: Mike Rapoport <[email-masked]>
Date: Wed, 17 Jul 2019 14:09:13 +0300

On Mon, Jun 24, 2019 at 06:51:21PM +0100, Catalin Marinas wrote:
> On Mon, Jun 24, 2019 at 04:32:53PM +0200, Andrey Konovalov wrote:
> > This patch is a part of a series that extends kernel ABI to allow to pass
> > tagged user pointers (with the top byte set to something else other than
> > 0x00) as syscall arguments.
> > 
> > userfaultfd code use provided user pointers for vma lookups, which can
> > only by done with untagged pointers.
> > 
> > Untag user pointers in validate_range().
> > 
> > Reviewed-by: Vincenzo Frascino <[email-masked]>
> > Reviewed-by: Catalin Marinas <[email-masked]>
> > Reviewed-by: Kees Cook <[email-masked]>
> > Signed-off-by: Andrey Konovalov <[email-masked]>
> > ---
> >  fs/userfaultfd.c | 22 ++++++++++++----------
> >  1 file changed, 12 insertions(+), 10 deletions(-)
> 
> Same here, it needs an ack from Al Viro.

The userfault patches usually go via -mm tree, not sure if Al looks at them :) 
 
FWIW, you can add 

Reviewed-by: Mike Rapoport <[email-masked]>

> > diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
> > index ae0b8b5f69e6..c2be36a168ca 100644
> > --- a/fs/userfaultfd.c
> > +++ b/fs/userfaultfd.c
> > @@ -1261,21 +1261,23 @@ static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx,
> >  }
> >  
> >  static __always_inline int validate_range(struct mm_struct *mm,
> > -					  __u64 start, __u64 len)
> > +					  __u64 *start, __u64 len)
> >  {
> >  	__u64 task_size = mm->task_size;
> >  
> > -	if (start & ~PAGE_MASK)
> > +	*start = untagged_addr(*start);
> > +
> > +	if (*start & ~PAGE_MASK)
> >  		return -EINVAL;
> >  	if (len & ~PAGE_MASK)
> >  		return -EINVAL;
> >  	if (!len)
> >  		return -EINVAL;
> > -	if (start < mmap_min_addr)
> > +	if (*start < mmap_min_addr)
> >  		return -EINVAL;
> > -	if (start >= task_size)
> > +	if (*start >= task_size)
> >  		return -EINVAL;
> > -	if (len > task_size - start)
> > +	if (len > task_size - *start)
> >  		return -EINVAL;
> >  	return 0;
> >  }
> > @@ -1325,7 +1327,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
> >  		goto out;
> >  	}
> >  
> > -	ret = validate_range(mm, uffdio_register.range.start,
> > +	ret = validate_range(mm, &uffdio_register.range.start,
> >  			     uffdio_register.range.len);
> >  	if (ret)
> >  		goto out;
> > @@ -1514,7 +1516,7 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
> >  	if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister)))
> >  		goto out;
> >  
> > -	ret = validate_range(mm, uffdio_unregister.start,
> > +	ret = validate_range(mm, &uffdio_unregister.start,
> >  			     uffdio_unregister.len);
> >  	if (ret)
> >  		goto out;
> > @@ -1665,7 +1667,7 @@ static int userfaultfd_wake(struct userfaultfd_ctx *ctx,
> >  	if (copy_from_user(&uffdio_wake, buf, sizeof(uffdio_wake)))
> >  		goto out;
> >  
> > -	ret = validate_range(ctx->mm, uffdio_wake.start, uffdio_wake.len);
> > +	ret = validate_range(ctx->mm, &uffdio_wake.start, uffdio_wake.len);
> >  	if (ret)
> >  		goto out;
> >  
> > @@ -1705,7 +1707,7 @@ static int userfaultfd_copy(struct userfaultfd_ctx *ctx,
> >  			   sizeof(uffdio_copy)-sizeof(__s64)))
> >  		goto out;
> >  
> > -	ret = validate_range(ctx->mm, uffdio_copy.dst, uffdio_copy.len);
> > +	ret = validate_range(ctx->mm, &uffdio_copy.dst, uffdio_copy.len);
> >  	if (ret)
> >  		goto out;
> >  	/*
> > @@ -1761,7 +1763,7 @@ static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx,
> >  			   sizeof(uffdio_zeropage)-sizeof(__s64)))
> >  		goto out;
> >  
> > -	ret = validate_range(ctx->mm, uffdio_zeropage.range.start,
> > +	ret = validate_range(ctx->mm, &uffdio_zeropage.range.start,
> >  			     uffdio_zeropage.range.len);
> >  	if (ret)
> >  		goto out;
> > -- 
> > 2.22.0.410.gd8fdbe21b5-goog

-- 
Sincerely yours,
Mike.

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